RT8859M
Application Information
complete fault protection functions including over voltage,
under voltage, negative voltage, over current and under
voltage lockout. The RT8859M is available in a WQFN-
56L 7x7 small footprint package.
The RT8859M is a CPU power controller which includes
two voltage rails : a 4/3/2/1 phase synchronous buck
controller, the CORE VR, and a single phase buck
controller, the AXG VR. The RT8859M is compliant with
Intel VR12/IMVP7 voltage regulator specification to fulfill
Intel's CPU power supply requirements of both CORE and
AXGvoltage rails. ASerial VID(SVID) interface is built-in
in the RT8859M to communicate with Intel VR12/IMVP7
compliant CPU.
General Loop Functions
VR Rail Addressing and Slew rate Setting
The voltage level at theADDpin defines the VR addresses
of the RT8859M. User can also flip the VR address by
properly setting the voltage on SR_ADDF pin. There are
three valid voltage levels forADDpin : VCC (5V), floating,
and GND. Connecting the ADD pin to one of these three
voltage levels can set the addresses of both CORE VR
andAXGVR according to the following table. TheAll Call
address, 1111, 1110, can only be used with SetVID or
SetPS commands.
The RT8859M adopts G-NAVPTM (Green Native AVP),
which is Richtek's proprietary topology derived from finite
DC gain compensator with current mode control, making
it an easy setting PWM controller, meeting all Intel CPU
requirements ofAVP (Active Voltage Positioning). The load
line can be easily programmed by setting the DC gain of
the error amplifier. The RT8859M has fast transient
response due to the G-NAVPTM commanding variable
switching frequency. Based on the G-NAVPTM topology,
the RT8859M also features a quick response mechanism
for optimizedAVP performance during load transient.
Address
Flip
VR1 (CORE) VR1 (AXG)
ADD Level
Address
Address
VCC
0100
0101
No
Floating
GND
0010
0011
TheG-NAVPTM topology also represents a high efficiency
system with green power concept. With the G-NAVPTM
topology, the RT8859M becomes a green power controller
with high efficiency under heavy load, light load, and very
light load conditions. The RT8859M supports mode
transition function with various operating states, including
multi-phase, single phase and diode emulation modes.
These different operating states allow the overall power
control system to have the lowest power loss. By utilizing
the G-NAVPTM topology, the operating frequency of the
RT8859M varies with VID, load, and input voltage to further
enhance the efficiency even in CCM.
0000
0001
VCC
0101
0100
Yes
Floating
GND
0011
0010
0001
0000
The RT8859M can also program the dynamic VID slew
rate by setting the SR_ADDF pin. After POR, the
RT8859M will detect the voltage level on the SR_ADDF
pin and latch the status of the address and the dynamic
VID slew rate. Below is the setting table of SR_ADDF.
The recommended voltage tolerance is (recommended
voltage 25mV). Make sure the voltage divider at
SR_ADDF pin uses the same VCC as pin 41 (VCC).
The built-in high accuracy DAC converts the SVID code
ranging from 0.25V to 1.52V with 5mV per step. The
RT8859M supports VID on-the-fly function with three
different slew rates : Fast, Slow andDecay. The RT8859M
also builds in a high accuracy ADC for some platform
setting functions, such as no-load offset or over-current
level. The controller supports bothDCR and sense resistor
current sensing. The RT8859M provides power VR ready
signals for both CORE VR and AXG VR. It also features
Copyright 2012 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
28
DS8859M-05 July 2012
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
